Ternary modulation using inter-operable transmitters and receivers

ABSTRACT

A ternary phase shift keying transmitter and receiver can efficiently communicate using ternary encoded data that avoids indistinguishable transition curves for each of the three modulated states in the ternary encoded data. The transmitter is interoperable and can function with different types of receivers including direct detection-based receivers and coherent detection-based receivers.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.17/224,507, filed Apr. 7, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/857,836, filed Apr. 24, 2020, which areincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure generally relates to signal processing, and moreparticularly to sending and receiving data.

BACKGROUND

Intensity modulation and direction detection (IM/DD) is widely used inshort-reach transmission systems. One type of IM/DD includes phase shiftkeying (PSK) in which the phase of the carrier wave is modulated with asignal to transmit data. Implementing different types of PSK on IM/DDsystems is difficult because of noise, signal loss, and phase detectionissues.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description includes discussion of figures havingillustrations given by way of example of implementations of embodimentsof the disclosure. The drawings should be understood by way of example,and not by way of limitation. As used herein, references to one or more“embodiments” are to be understood as describing a particular feature,structure, or characteristic included in at least one implementation ofthe inventive subject matter. Thus, phrases such as “in one embodiment”or “in an alternate embodiment” appearing herein describe variousembodiments and implementations of the inventive subject matter, and donot necessarily all refer to the same embodiment. However, they are alsonot necessarily mutually exclusive. To easily identify the discussion ofany particular element or act, the most significant digit or digits in areference number refer to the figure (“FIG.”) number in which thatelement or act is first introduced.

FIG. 1 shows an example architecture of a phase shift keying transmitterand receiver, according to some example embodiments.

FIGS. 2A-2D show example ternary and quaternary constellationeyediagrams, according to some example embodiments.

FIG. 3 shows a mapping architecture for converting TPSK fortransmission, according to some example embodiments.

FIGS. 4A and 4B show example sampling configurations, according to someexample embodiments.

FIG. 5 shows an example transmitter and receiver, according to someexample embodiments.

FIG. 6 shows an example direct detection TPSK communicationarchitecture, according to some example embodiments.

FIG. 7 shows an example hybrid TPSK communication architecture,according to some example embodiments.

FIG. 8 shows an example coherent detection based TPSK communicationarchitecture, according to some example embodiments.

FIG. 9 shows an example TPSK data center architecture, according to someexample embodiments.

FIG. 10 shows a flow diagram of an example method for implementing aTPSK transmitter, according to some example embodiments.

FIG. 11 shows a flow diagram of an example method for implementing aTPSK receiver, according to some example embodiments.

FIG. 12 shows an example system for implementing a ternary data scheme,according to some example embodiments.

Descriptions of certain details and implementations follow, including adescription of the figures, which may depict some or all of theembodiments described below, as well as discussing other potentialembodiments or implementations of the inventive concepts presentedherein. An overview of embodiments of the disclosure is provided below,followed by a more detailed description with reference to the drawings.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide an understanding ofvarious embodiments of the inventive subject matter. It will be evident,however, to those skilled in the art, that embodiments of the inventivesubject matter may be practiced without these specific details. Ingeneral, well-known instruction instances, structures, and techniquesare not necessarily shown in detail.

Generally, intensity modulation/direct detection is common in someshort-reach transmission systems. One approach includes on-off keying(OOK), which is among the oldest modulation formats used in opticalIM/DD systems that still remains popular due to its low implementationcost. However, the 1-bit carrying OOK format cannot meet theever-increasing bandwidth requirement in today's information society.4-level pause amplitude modulation (PAM4), which carries 2 bits persymbol, has been proposed and commercially implemented inintra/inter-data center networks. However, lots of optics manufacturersuse a wait-and-see approach about the mass production of PAM4transceivers, especially in the application of beyond 40 km reach.Accordingly, OOK cannot meet modern bandwidth requirements, coherentsolution approaches are still too expensive to be commercially deployedin inter/intra-date center networks, and PAM4 solutions are not easilyupgradable to coherent solutions in the future and thus may become outof date and impractical as technology evolves.

To this end, a ternary phase shift keying (TPSK) based opticalcommunication system can be implemented to transmit and receive data inTPSK format. In some example embodiments, the binary data is convertedinto TPSK symbols using a distribution matcher to generate TPSK sequencedata. The TPSK data can be mapped to a non-TPSK format that is easy totransmit over existing systems (e.g., existing binary systems). Forexample, the TPSK data is mapped to QPSK data using a phase mapping.Further, forward error correction can be implemented by converting thesymbol data into binary data for forward error correction, thenconverting it back into the symbol data for transmission.

In some example embodiments, the data is transmitted over a single modefiber to a receiver, which can use various detection schemes, such asdirect or coherent detection, to detect the signal. The received signaldata can be sampled at transient time between the symbol segments usingan analog-to-digital converter and channel equalizer. The sampled QPSKsymbol data can be converted into binary data for forward errorcorrection decoded, and then mapped back TPSK data using the QPSK toTPSK phase mapping. Further, the receiver implements an inversedistribution matching module to recover and store the binary messagedata.

The TPSK-based optical communication system provides benefits overtraditional OOK because it carries more bits per symbol than traditionalOOK. Further, the TPSK-based optical communication system is easier toupgrade to coherent solutions than PAM4 while still being compatiblewith a traditional OOK-based system. Further, users implementing thesystem can select coherent detection and/or direct detection as pertheir requirements, so the proposed solution can meet the diverse marketrequirements. Additionally, the interoperable transmitter of the TPSKsystem can be readily adapted for use with newer detection schemes.

FIG. 1 shows an example architecture 100 of a phase shift keyingtransmitter and receiver, according to some example embodiments. In thetransmitter 105, binary data can be modulated using phase modulation ofan optical carrier (e.g., light). The modulated signal is then boostedusing an amplifier (e.g., EDFA) and transmitted to the receiver over atransmission architecture 110, such as a network, in open air as radiowaves, or an optical medium such as single mode fiber 115 (SMF) withseveral amplifiers. In the receiver 120, the received optical signal isrecovered and translated back into the binary data for output.

FIGS. 2A-2D show example constellation and eyediagrams, according tosome example embodiments. FIG. 2A displays a quaternary constellationdiagram and FIG. 2B displays a quaternary eyediagram that corresponds tothe quaternary constellation diagram of FIG. 2A. FIG. 2C displays aternary constellation diagram and FIG. 2D displays a ternary eyediagramthat corresponds to the ternary constellation diagram of FIG. 2C.

A constellation diagram (e.g., FIG. 2A, FIG. 2C) is a representation ofa signal modulated by a digital modulation scheme (e.g., quadratureamplitude-based modulation, quaternary phase-shift keying, ternary phaseshift keying, and so on). Constellation diagrams display the signal as atwo-dimensional XY-plane scatter diagram in the complex plane at symbolsampling instants. The angle of a point, measured counterclockwise fromthe horizontal axis, represents the phase shift of the carrier wave froma reference phase. The distance of a point from the origin represents ameasure of the amplitude or power of the signal.

An eyediagram (e.g., FIG. 2B, FIG. 2D) is an example signal detectiondisplay (e.g., oscilloscope display) in which a signal from a receiveris repetitively sampled and applied to the vertical input, while thedata rate is used to trigger the horizontal sweep.

In the constellation diagram of FIG. 2A, the four symbols (e.g., modes,states) of the quaternary scheme include “0”, “1”, “2”, and “3”, each ofwhich corresponds to a phase and amplitude for the given symbol. Asdiscussed, if quaternary modulation is implemented, phase loss can occurand some transitions between the symbols will become indistinguishablefrom one another.

For example, in FIG. 2A, the transition from symbol “0” to “0”corresponds to a curve 200 in the eyediagram of FIG. 2B, which isdistinguishable from the other curves in FIG. 2B. Further, again withreference to FIG. 2A, the transition from “0” to “3” corresponds to acurve 205 in the eyediagram of FIG. 2B, which is again distinguishablefrom the other curves in FIG. 2B.

However, when using direct detection, some quaternary scheme transitionswill be degenerate in that they are indistinguishable from one anotherand have approximately the same transition curve in the detecteddisplays (e.g., eyediagram of FIG. 2B). In particular, for example, inFIG. 2A, the transition from “0” to “1” and the transition from “0” to“2” both result in curve 210 in the eyediagram of FIG. 2B. Thus, as thetwo are indistinguishable, systemic errors will occur in of the QPSKdata when transmitted and received (e.g., using direct detection).

To this end, a ternary phase shift keying scheme can be implemented toavoid indistinguishable phases and errors. In particular, as illustratedin the constellation diagram in FIG. 2C, a ternary phase shift keyingscheme includes three symbols (modes) including “0”, “1”, and “2”;however, no mode is implemented in the bottom left had quadrant (asdenoted by the non-solid circle 213 in FIG. 2C), thereby avoidingdegenerate phases.

For example, in FIG. 2C, the transition from symbol “0” to “0”corresponds to a curve 215 in the eyediagram of FIG. 2D, which isdistinguishable from the other curves in FIG. 2D. Further, again withreference to FIG. 2C, the transition from “0” to “2” corresponds tocurve 220 in the eyediagram of FIG. 2D, and the transition from “0” to1” (in FIG. 2C) corresponds to curve 225 (in FIG. 2D). As illustrated inFIG. 2D, no transitions overlap and thus they can be distinguished(e.g., when transitions are detected using direct detection), andthereby properly decoded without systemic error.

FIG. 3 shows a mapping architecture 300 for converting TPSK to anon-TPSK format (e.g., QPSK, binary PSK, additional higher order PSKformats) for transmission, according to some example embodiments. Asdiscussed with reference to FIG. 2A-2D above, implementing TPSK canavoid errors by using curves that are distinguishable by the receiverdetector (e.g., in direct detection, a fast photo diode). To facilitatetransmission of TPSK-encoded data over existing networks (e.g., binarynetworks configured to transmit data in 1's and 0's), the TPSK data isconverted to QPSK data for transmission and then converted back intoTPSK at the receiver, in accordance with some example embodiments.

The example displayed in FIG. 3 shows example mapping from TPSK to QPSKfor transmission, where the reverse mapping process can then be used atthe receiver to convert received QPSK data back into TPSK data forfurther processing (e.g., sampling, ternary based decoding).

As illustrated, the eyediagram 305 displays a ternary encoding schemefor TPSK symbols. In the example, the TPSK symbols—1, 0, 2, 2, 1,1—create curve mappings on the diagram 305, where “0” corresponds to nochange and no turning (e.g., can be displayed as a loop back to the samesymbol), “1” corresponds to turning 90 degrees clockwise, and “2”corresponds to turning 180 degrees clockwise.

In the illustrated example, starting from the top left symbol (“STARTHERE”), the first TPSK symbol is “1,” (from the TPSK symbols) which is a90-degree turn to the top-right point (corresponding to mapping arrow310). The second TPSK symbol is “0”, which is a repeat symbol back tothe top-right point (corresponding to mapping arrow 307). The third TPSKsymbol is “2,” which is a 180-degree turn to the bottom left symbol(corresponding to mapping arrow 313). The third symbol is another 2,which is another 180-degree turn back to the top right symbol(corresponding to mapping arrow 315). The fourth symbol is a “1,” whichis a 90-degree turn from the top right symbol to the bottom right symbol(corresponding to mapping arrow 320). The fifth symbol is another “1,”which is a 90-degree turn from the bottom right to bottom left symbol(corresponding to mapping arrow 325).

To generate the QPSK symbols, the mapping 330 from the TPSK symbolsequence is then applied to the QPSK constellation diagram 335, in whichthe top left symbol is “0”, the top right symbol is “1”, the bottomright symbol is “2” and the bottom left symbol is “3”. That is, inparticular, the mapping 330 starts from the top left symbol so the QPSKsymbols start with “0”, followed by “1”, followed by a repeat “1” due tothe looped curve 307, and so on.

In the example of FIG. 3, the starting point is the top left symbol,which generates a starting “0” in the QPSK symbol sequence. However, itis not necessary to always start from the top-left symbol; any point canbe used. For the decoding purpose (e.g., at the receiver), there can bean indicator (e.g., stored in memory or decoding instructions) to showwhere the symbols start from. Therefore, if starting from 0, the QPSKsymbols will lead with a 0; if starting from 2, the QPSK symbols willlead with a 2, and so on.

Additionally, the TPSK symbols can be converted to other formats, otherthan QPSK (e.g., binary PSK (BPSK)), for transmission across a network,according to some example embodiments. That is, for example, a higherorder PSK format having 8 states or modes can be mapped to (from TPSK)using different phase shifts per TPSK symbol. For instance, while theabove example for QPSK uses no turn for “0”, 90 degree turn for “1”, and180 degree turn for “2”, the amount of turn per TPSK signal can becustomized to work for higher order PSK schemes (e.g., an 8 mode scheme)by turning by different amounts per TPSK symbol (e.g., 20 degrees for“0”, 100 degree turn for “1” and 270 degree turn “2” of the TPSKsignals), such that the mapping created maps TPSK to different modes ofthe higher order PSK scheme, or lower order scheme (e.g., BPSK),according to some example embodiments.

FIGS. 4A and 4B show example sampling configurations, according to someexample embodiments. Generally, QPSK symbols can only be detected bycoherent detection, where symbol sampling occurs at the center of symboltime as non-center sampling locations incur signal-to-noise ratioissues. However, sampling at center symbol time using the TPSK schemecan result in loss in information. For example, in the sampling graph400 of FIG. 4A, the center sampled point 405 may miss the data to bedetected. In contrast, as shown in FIG. 4B, in sampling graph 410, thesampling of ternary data is implemented at transient time (e.g.,transition points between symbols), and each signal can be sampled forthe TPSK data as illustrated by sampling point 415.

FIG. 5 shows an example transmitter 500 and receiver 550, according tosome example embodiments. In the example of FIG. 5, the components ofthe transmitter 500 and receiver can be implemented using software(applications, non-transitory instructions stored in memory), hardware(e.g., servers, switches), electrical devices (e.g., chips, controlcircuitry, an Field Programmable Gate Array), optical devices (e.g.,lasers, fiber cables, photodiodes) and combinations thereof. In thetransmitter 500, one or more light sources, such as laser 502, cangenerate binary data 504. In some example embodiments, the binary data504 is not generated by the light sources, but is rather received froman external source not depicted in FIG. 5, such as a fiber from anothercomponent, or may be identified as binary data stored in memory andready for transmission via the transmitter 500.

The binary data 504 is input into a distribution matcher 506 (e.g., aconstant composition distribution (CCDM) based distribution matcher),which is configured to efficiently convert binary data to a symbolsequence following any entropy, including for example a ternary symbolscheme (e.g., three symbols: 1, 2, 3). The distribution matcher 506 (DM)encodes a binary input data sequence into a sequence of symbols(codewords), with desired target probability distribution. In someexample embodiments, the distribution matcher 506 uses a CCDM version ofdistribution matching to map the binary data 504 to 0, 1, 2 ternarysymbols, where each symbol is generated with equal probability (1/3). Insome example embodiments, it is not necessary to generate each of thethree symbols with equal likelihood. For example, the distributionmatcher 506 can implement an exponential distribution to generate a morepower-efficient modulation format, according to some exampleembodiments. The set of the output codewords constitutes a codebook (orcode) of the DM 506. Further, constant-composition DM (CCDM) usesarithmetic coding to efficiently encode data into codewords from aconstant-composition (CC) codebook, which can be implemented to decodethe symbols back into binary data using inverse distribution matcher 566in the receiver 550.

The TPSK data from the distribution matcher 506 is then input into theTPSK-QPSK converter 508, which converts the TPSK symbol data into QPSKsymbol data, as discussed above with reference to FIG. 3.

The QPSK symbols output by the TPSK-QPSK converter 508 are thenconverted into bits using a bit labeling module 510. For example, withreference to the constellation diagram 335 in FIG. 3, if the QPSK symbolis “1,” it is converted into binary “01” by the bit labeling module 510.

The bit data is then input into forward error correction (FEC) codingmodule 512 for error correction processing. Generally, forward errorcorrection is a technique used for controlling errors in datatransmission over unreliable or noisy communication channels. In FEC,the transmitter encodes the message in a redundant way, most often byusing an error-correcting code (ECC). The redundancy allows the receiverto detect a number of errors that may occur anywhere in the message(e.g., errors accumulated while in transit), and often to correct theseerrors without re-transmission.

FEC enables the receiver the ability to correct errors without needing areverse channel to request re-transmission of data. In some exampleembodiments, non-binary FEC is implemented; however, non-binary FEC iscomplex and can be difficult to implement. In the illustratedembodiment, the QPSK data has already been converted into binary dataand thus a binary FEC scheme can be beneficially implemented by thetransmitter 500 and receiver 550. The FEC coding module 512 outputsbinary data, which is then input into binary-to-symbol (B2S) mappingmodule 514 for conversion back into QPSK symbols.

The data is then input into a pre-compiler CD 516 for processing,followed by a digital-to-analog converter 518 (DAC), which then convertsthe data into analog data, which is then transmitted via I/Q modulator520 using laser 502.

The data is transmitted from the transmitter 500 to the receiver 550over transmission architecture 552, such as a single mode fiber (SMF)and one or more amplifiers (e.g., erbium-doped fiber amplifier (EDFA))to boost the signal along the way.

At the receiver 550, a detector 553 receives the data from thetransmission architecture 552 (e.g., as analog signal). Notably, thedetector 553 can be a direct detection (DD)—based detector or coherentdetection-based detector, either of which will work with transmitter 500without requiring a matching transmitter type, as discussed in furtherdetail below with reference to FIGS. 6-9.

The detector 553 outputs the analog data into an analog-to-digitalconverter (ADC) 554, which initially samples the analog data, and thenthe optimal transient points are obtained by re-sampling algorithmsusing the channel equalizer 556 to generate QPSK data. The data is thenconverted from QPSK symbols into binary data by symbol-to-binary (S2B)mapping module 558 for binary-based error correction using the FECdecoding module 560. The FEC decoding module 560 performs binary-basederror correction decoding, and then outputs the binary data into S2Bmapping module 562. The binary data is then converted into QPSK symbolsby the S2B mapping module 562 and then converted into TPSK symbols usingQPSK-TPSK converter 564. For example, the QPSK-TPSK converter 564 usesthe reverse of the process discussed with reference to FIG. 3 above(e.g., mapping QPSK curves to TPSK data). The TPSK symbols are output bythe QPSK-TPSK converter 564, and then converted from ternary symbolsinto binary data using an inverse distribution matcher 566 discussedabove, which then outputs binary data 568 for further process or storage(e.g., in memory).

One benefit of the TPSK scheme of FIG. 5 is that the transmitter (e.g.,transmitter 500) is interoperable with different types of receivers.This enables a single transmitter to function with the current state ofthe art (e.g., direct detection systems) and advances to such systems,such as coherent detection systems, which rolled out while requiringminimal or no changes to the TPSK transmitters. FIGS. 6-10 show examplesof interoperable transmitter and receiver configurations, according tosome example embodiments.

FIG. 6 shows an example direct detection (DD) TPSK communicationarchitecture 600, according to some example embodiments. In theillustrated example, the TPSK transceiver 605 and TPSK transceiver 610both include a TPSK transmitter (Tx), such as transmitter 500. Further,each of TPSK transceivers 605 and 610 includes direct detection-basedreceivers (D-Rx). For example, both of the both of TPSK transceivers 605and 610 include a direct detection version of detector 553 in FIG. 6.

FIG. 7 shows an example hybrid TPSK communication architecture 700,according to some example embodiments. In the illustrated example, theTPSK transceiver 705 and TPSK transceiver 710 both include a TPSKtransmitter (Tx), such as transmitter 500. However, the transceivers705, 710 have different types of receiver modules. For example, thetransceiver 705 may have upgraded to a coherent detection-based receiver(C-Rx), while the transceiver 710 retains its detection-based receiver(D-Rx). However, due to the interoperable TPSK architecture (e.g.,transmitter 500 of FIG. 5), the transceiver 710 does not need to modifyits transmitter to work with the coherent detection-based receiver oftransceiver 705 and can use its same transmitter with any otherTPSK-based receiver, whether it is a direct detection-based receiver orcoherent detection-based receiver.

FIG. 8 shows an example coherent detection based TPSK communicationarchitecture 800, according to some example embodiments. In theillustrated example, the TPSK transceiver 805 and TPSK transceiver 810both include a TPSK transmitter (Tx), such as transmitter 500. Further,the transceivers 805, 810 have the same type of receivers, i.e.,coherent-based receivers (e.g., C-Rx). For example, both transceivers805, 810 have upgraded to coherent detection-based detectors in theirreceiver modules. Further, while coherent detection-based receivers arediscussed as an example of an upgraded receiver, the architecture ofTPSK transmitter (e.g., transmitter 500) removes the emphasis onreceiver type, thereby allowing future receiver types to be integratedinto the TPSK architecture to allow future upgradeability.

FIG. 9 shows an example TPSK data center architecture 900, according tosome example embodiments. As illustrated, data center 905 comprises TPSKtransceiver 915, TPSK transceiver 920, and TPSK transceiver 925. Datacenter 910 is a separate data center (e.g., a data center at a differentgeographic location) and comprises TPSK transceiver 930, TPSKtransceiver 935, and TPSK transceiver 940. Each data center 905, 910 canuse its TPSK transceivers to communicate data with other transceivers,each of which may have different receiver types (e.g., direct detection,coherent detection, etc.) but can still implement the same interoperableTPSK transmitter. For example, TPSK transceiver 930 can use its TPSKtransmitter (Tx 4) to send TPSK data (e.g., TPSK data in non-TPSKformat) to the coherent detection-based receiver (C-Rx 2) in transceiver920. Similarly, TPSK transceiver 920 uses its interoperable TPSKtransmitter (Tx 2) to send data to a direct detection-based receiver(D-Rx 1) in the TPSK transceiver 915, which is located in the same datacenter 905; further, TPSK transceiver 920 can also use its same TPSKtransmitter (Tx 2) to send an inter-data center link communication totransceiver 930, which receives the data using a coherentdetection-based receiver (C-Rx 4). Thus, as illustrated, not allreceivers need be of the same exact type; different receiver types canbe used, and they can be upgraded at different points in time and stillreceive the TPSK data in an efficient and robust manner.

FIG. 10 shows a flow diagram of an example method 1000 for implementinga TPSK transmitter (e.g., transmitter 500), according to some exampleembodiments. At operation 1005, the TPSK transmitter 500 generatesbinary data. For example, the TPSK transmitter 500 generates binary datausing a light source. According to some alternative embodiments, thedata may be identified instead of generated at operation 1005. That is,for example, the binary data has already been generated and is stored inmemory of the transmitter ready for encoding and transmission.

At operation 1010, the TPSK transmitter 500 generates TPSK data. Forexample, the TPSK transmitter 500 uses a distribution matcher to convertthe binary data into ternary symbols, e.g., 0, 1, 2, using an equaldistribution likelihood.

At operation 1015, the TPSK transmitter 500 converts the TPSK data totransmission format. For example, the TPSK transmitter 500 maps the TPSKsymbol sequence into a non-TPSK format, such as a QPSK symbol sequence,as discussed above. Additionally, and in accordance with some exampleembodiments, the generated QPSK symbols are then converted into bits forFEC coding, and then converted back into QPSK for transmission.

At operation 1020, the TPSK transmitter 500 transmits non-TPSK data toits destination. For example, the TPSK transmitter 500 transmits thedata in the non-TPSK format to the receiver 550 over a single mode fiberboosted by one or more amplifiers.

FIG. 11 shows a flow diagram of an example method 1100 for implementinga TPSK-based receiver, according to some example embodiments.

At operation 1105, the TPSK receiver 550 receives data in the non-TPSKformat. For example, the TPSK receiver 550 uses direct detection-basedsystem to receive the data. Alternatively, the TPSK receiver 550 uses acoherent detection-based receiver or other types of receiver detectors,such as antennas, to receive the data.

At operation 1110, the TPSK receiver 550 samples the received data attransient time. For example, the data is received as an analog signal,which is then first sampled by an analog-to-digital converter (ADC).Then the optimal transient points are obtained by implementingre-sampling in the channel equalization module in the receiver.

At operation 1115, the TPSK receiver 550 converts the sampled non-TPSKdata to TPSK data. For example, the non-TPSK sampled data can be data inthe QPSK format. The QPSK data is then converted into binary data toundergo binary FEC decoding and is then converted back into the QPSKdata. After binary-based error correction, the QPSK data is thenconverted into TPSK data using a phase mapping as discussed in FIG. 3above. For example, the QPSK data sequence curves are mapped to a TPSKconstellation diagram to generate the TPSK data.

At operation 1120, the TPSK receiver 550 converts the TPSK data intobinary data. For example, the TPSK receiver 550 implements an inversedistribution matcher using the same codebook as the distribution matcherin the transmitter 500 to convert the TPSK symbols into binary data.

FIG. 12 illustrates a diagrammatic representation of a machine 1200 inthe form of a computer system within which a set of instructions may beexecuted for causing the machine to perform any one or more of themethodologies discussed herein, according to an example embodiment.Specifically, FIG. 12 shows a diagrammatic representation of the machine1200 in the example form of a computer system, within which instructions1216 (e.g., software, a program, an application, an applet, an app, orother executable code) for causing the machine 1200 to perform any oneor more of the methodologies discussed herein may be executed. Forexample, the instructions 1216 may cause the machine 1200 to execute themethod 1000 of FIG. 10 (as a transmitter) and/or execute the 1100 ofFIG. 11 (as a receiver). Additionally, or alternatively, theinstructions 1216 may implement the transmitter 500 or the receiver 550in FIG. 5, and so forth. The instructions 1216 transform the general,non-programmed machine 1200 into a particular machine 1200 programmed tocarry out the described and illustrated functions in the mannerdescribed. In alternative embodiments, the machine 1200 operates as astandalone device or may be coupled (e.g., networked) to other machines.In a networked deployment, the machine 1200 may operate in the capacityof a server machine or a client machine in a server-client networkenvironment, or as a peer machine in a peer-to-peer (or distributed)network environment. The machine 1200 may comprise, but not be limitedto, a server computer, a client computer, a personal computer (PC), atablet computer, a laptop computer, a netbook, a set-top box (STB), aPDA, an entertainment media system, a cellular telephone, a smart phone,a mobile device, a wearable device (e.g., a smart watch), a smart homedevice (e.g., a smart appliance), other smart devices, a web appliance,a network router, a network switch, a network bridge, or any machinecapable of executing the instructions 1216, sequentially or otherwise,that specify actions to be taken by the machine 1200. Further, whileonly a single machine 1200 is illustrated, the term “machine” shall alsobe taken to include a collection of machines 1200 that individually orjointly execute the instructions 1216 to perform any one or more of themethodologies discussed herein.

The machine 1200 may include processors 1210, memory 1230, and I/Ocomponents 1250, which may be configured to communicate with each othersuch as via a bus 1202. In an example embodiment, the processors 1210(e.g., a Central Processing Unit (CPU), a Reduced Instruction SetComputing (RISC) processor, a Complex Instruction Set Computing (CISC)processor, a Graphics Processing Unit (GPU), a Digital Signal Processor(DSP), an ASIC, a Radio-Frequency Integrated Circuit (RFIC), anotherprocessor, or any suitable combination thereof) may include, forexample, a processor 1212 and a processor 1214 that may execute theinstructions 1216. The term “processor” is intended to includemulti-core processors that may comprise two or more independentprocessors (sometimes referred to as “cores”) that may executeinstructions contemporaneously. Although FIG. 12 shows multipleprocessors 1210, the machine 1200 may include a single processor with asingle core, a single processor with multiple cores (e.g., a multi-coreprocessor), multiple processors with a single core, multiple processorswith multiples cores, or any combination thereof.

The memory 1230 may include a main memory 1232, a static memory 1234,and a storage unit 1236, both accessible to the processors 1210 such asvia the bus 1202. The main memory 1230, the static memory 1234, andstorage unit 1236 store the instructions 1216 embodying any one or moreof the methodologies or functions described herein. The instructions1216 may also reside, completely or partially, within the main memory1232, within the static memory 1234, within the storage unit 1236,within at least one of the processors 1210 (e.g., within the processor'scache memory), or any suitable combination thereof, during executionthereof by the machine 1200.

The I/O components 1250 may include a wide variety of components toreceive input, provide output, produce output, transmit information,exchange information, capture measurements, and so on. The specific I/Ocomponents 1250 that are included in a particular machine will depend onthe type of machine. For example, portable machines such as mobilephones will likely include a touch input device or other such inputmechanisms, while a headless server machine will likely not include sucha touch input device. It will be appreciated that the I/O components1250 may include many other components that are not shown in FIG. 12.The I/O components 1250 are grouped according to functionality merelyfor simplifying the following discussion and the grouping is in no waylimiting. In various example embodiments, the I/O components 1250 mayinclude output components 1252 and input components 1254. The outputcomponents 1252 may include visual components (e.g., a display such as aplasma display panel (PDP), a light emitting diode (LED) display, aliquid crystal display (LCD), a projector, or a cathode ray tube (CRT)),acoustic components (e.g., speakers), haptic components (e.g., avibratory motor, resistance mechanisms), other signal generators, and soforth. The input components 1254 may include alphanumeric inputcomponents (e.g., a keyboard, a touch screen configured to receivealphanumeric input, a photo-optical keyboard, or other alphanumericinput components), point-based input components (e.g., a mouse, atouchpad, a trackball, a joystick, a motion sensor, or another pointinginstrument), tactile input components (e.g., a physical button, a touchscreen that provides location and/or force of touches or touch gestures,or other tactile input components), audio input components (e.g., amicrophone), and the like.

In further example embodiments, the I/O components 1250 may includebiometric components 1256, motion components 1258, environmentalcomponents 1260, or position components 1262, among a wide array ofother components. For example, the biometric components 1256 may includecomponents to detect expressions (e.g., hand expressions, facialexpressions, vocal expressions, body gestures, or eye tracking), measurebiosignals (e.g., blood pressure, heart rate, body temperature,perspiration, or brain waves), identify a person (e.g., voiceidentification, retinal identification, facial identification,fingerprint identification, or electroencephalogram-basedidentification), and the like. The motion components 1258 may includeacceleration sensor components (e.g., accelerometer), gravitation sensorcomponents, rotation sensor components (e.g., gyroscope), and so forth.The environmental components 1260 may include, for example, illuminationsensor components (e.g., photometer), temperature sensor components(e.g., one or more thermometers that detect ambient temperature),humidity sensor components, pressure sensor components (e.g.,barometer), acoustic sensor components (e.g., one or more microphonesthat detect background noise), proximity sensor components (e.g.,infrared sensors that detect nearby objects), gas sensors (e.g., gasdetection sensors to detection concentrations of hazardous gases forsafety or to measure pollutants in the atmosphere), or other componentsthat may provide indications, measurements, or signals corresponding toa surrounding physical environment. The position components 1262 mayinclude location sensor components (e.g., a GPS receiver component),altitude sensor components (e.g., altimeters or barometers that detectair pressure from which altitude may be derived), orientation sensorcomponents (e.g., magnetometers), and the like.

Communication may be implemented using a wide variety of technologies.The I/O components 1250 may include communication components 1264operable to couple the machine 1200 to a network 1280 or devices 1270via a coupling 1282 and a coupling 1272, respectively. For example, thecommunication components 1264 may include a network interface componentor another suitable device to interface with the network 1280. Infurther examples, the communication components 1264 may include wiredcommunication components, wireless communication components, cellularcommunication components, Near Field Communication (NFC) components,Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components,and other communication components to provide communication via othermodalities. The devices 1270 may be another machine or any of a widevariety of peripheral devices (e.g., a peripheral device coupled via aUSB).

Moreover, the communication components 1264 may detect identifiers orinclude components operable to detect identifiers. For example, thecommunication components 1264 may include Radio Frequency Identification(RFID) tag reader components, NFC smart tag detection components,optical reader components (e.g., an optical sensor to detectone-dimensional bar codes such as Universal Product Code (UPC) bar code,multi-dimensional bar codes such as Quick Response (QR) code, Azteccode, Data Matrix, Dataglyph, MaxiCode, PDF417, Ultra Code, UCC RSS-2Dbar code, and other optical codes), or acoustic detection components(e.g., microphones to identify tagged audio signals). In addition, avariety of information may be derived via the communication components1264, such as location via Internet Protocol (IP) geolocation, locationvia Wi-Fi® signal triangulation, location via detecting an NFC beaconsignal that may indicate a particular location, and so forth.

The various memories (i.e., 1230, 1232, 1234, and/or memory of theprocessor(s) 1210) and/or storage unit 1236 may store one or more setsof instructions and data structures (e.g., software) embodying orutilized by any one or more of the methodologies or functions describedherein. These instructions (e.g., the instructions 1216), when executedby processor(s) 1210, cause various operations to implement thedisclosed embodiments.

As used herein, the terms “machine-storage medium,” “device-storagemedium,” “computer-storage medium” mean the same thing and may be usedinterchangeably in this disclosure. The terms refer to a single ormultiple storage devices and/or media (e.g., a centralized ordistributed database, and/or associated caches and servers) that storeexecutable instructions and/or data. The terms shall accordingly betaken to include, but not be limited to, solid-state memories, andoptical and magnetic media, including memory internal or external toprocessors. Specific examples of machine-storage media, computer-storagemedia and/or device-storage media include non-volatile memory, includingby way of example semiconductor memory devices, e.g., erasableprogrammable read-only memory (EPROM), electrically erasableprogrammable read-only memory (EEPROM), Field Programmable Gate Array(FPGA), and flash memory devices; magnetic disks such as internal harddisks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROMdisks. The terms “machine-storage media,” “computer-storage media,” and“device-storage media” specifically exclude carrier waves, modulateddata signals, and other such media, at least some of which are coveredunder the term “signal medium” discussed below.

In various example embodiments, one or more portions of the network 1280may be an ad hoc network, an intranet, an extranet, a VPN, a LAN, aWLAN, a WAN, a WWAN, the Internet, a portion of the Internet, a portionof the PSTN, a plain old telephone service (POTS) network, a cellulartelephone network, a wireless network, a Wi-Fi® network, another type ofnetwork, or a combination of two or more such networks. For example, thenetwork 1280 or a portion of the network 1280 may include a wireless orcellular network, and the coupling 1282 may be a Code Division MultipleAccess (CDMA) connection, a Global System for Mobile communications(GSM) connection, or another type of cellular or wireless coupling. Inthis example, the coupling 1282 may implement any of a variety of typesof data transfer technology, such as Single Carrier Radio TransmissionTechnology (1×RTT), Evolution-Data Optimized (EVDO) technology, GeneralPacket Radio Service (GPRS) technology, Enhanced Data rates for GSMEvolution (EDGE) technology, third Generation Partnership Project (3GPP)including 3G, fourth generation wireless (4G) networks, Universal MobileTelecommunications System (UMTS), High Speed Packet Access (HSPA),Worldwide Interoperability for Microwave Access (WiMAX), Long TermEvolution (LTE) standard, others defined by various standard-settingorganizations, other long range protocols, or other data transfertechnology.

The instructions 1216 may be transmitted or received over the network1280 using a transmission medium via a network interface device (e.g., anetwork interface component included in the communication components1264) and utilizing any one of a number of well-known transfer protocols(e.g., hypertext transfer protocol (HTTP)). Similarly, the instructions1216 may be transmitted or received using a transmission medium via thecoupling 1272 (e.g., a peer-to-peer coupling) to the devices 1270. Theterms “transmission medium” and “signal medium” mean the same thing andmay be used interchangeably in this disclosure. The terms “transmissionmedium” and “signal medium” shall be taken to include any intangiblemedium that is capable of storing, encoding, or carrying theinstructions 1216 for execution by the machine 1200, and includesdigital or analog communications signals or other intangible media tofacilitate communication of such software. Hence, the terms“transmission medium” and “signal medium” shall be taken to include anyform of modulated data signal, carrier wave, and so forth. The term“modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a matter as to encode informationin the signal.

The terms “machine-readable medium,” “computer-readable medium” and“device-readable medium” mean the same thing and may be usedinterchangeably in this disclosure. The terms are defined to includeboth machine-storage media and transmission media. Thus, the termsinclude both storage devices/media and carrier waves/modulated datasignals.

The following are example embodiments:

Example 1. A method for processing optical data using a phase shift key(PSK) transmitter comprising: identifying binary data for transmission;generating ternary modulated data from the binary data, the ternarymodulated data being in a ternary PSK format comprising three modulationstates; generating, from the ternary modulated data, non-ternarymodulated data for transmission to a receiver, the non-ternary modulateddata being in a non-ternary PSK format that comprises more than threemodulation states; and transmitting, to the receiver, the non-ternarymodulated data as light using an optical source.

Example 2. The method of example 1, wherein converting the ternarymodulated data to the non-ternary modulated data comprises using a phasemapping to map the ternary PSK format to the non-ternary PSK format.

Example 3. The method of any one of examples 1 to 2, wherein thenon-ternary PSK format is a quaternary PSK format comprising fourmodulation states.

Example 4. The method of any one of examples 1-3, wherein the receiveris a direct detection based receiver that receives the light comprisingthe non-ternary modulated data.

Example 5. The method of any one of examples 1-4, wherein the receiveris a coherent detection based receiver that receives the lightcomprising the non-ternary modulated data.

Example 6. The method of any one of examples 1-5, wherein the receiveris configured to sample the received light at transient time, thesampling at transient time being performed by an analog-to-digitalconverter in the receiver.

Example 7. The method of any one of examples 1-6, wherein transient timecorresponds to points between symbol segments of the received light.

Example 8. The method of any one of examples 1-7, further comprising:converting the non-ternary modulated data into light using the opticalsource, wherein the light is transmitted to the receiver using a fiber.

Example 9. The method of any one of examples 1-8, wherein the fiber is asingle mode fiber.

Example 10. The method of any one of examples 1-9, wherein thenon-ternary modulated data is converted to analog data using adigital-to-analog converter.

Example 11. The method of any one of examples 1-10, wherein the ternarymodulated data is generated from the binary data using a distributionmatcher.

Example 12. The method of any one of examples 1-11, wherein thedistribution matcher is a constant composition distribution matcher.

Example 13. The method of any one of examples 1-12, wherein the receiveris configured to convert the light into ternary modulated data andconvert the ternary modulated data into the binary data using an inversedistribution matcher.

Example 14. The method of any one of examples 1-13, further comprising:converting the non-ternary modulated data into binary data; generatingforward error correction (FEC) binary data by applying FEC coding to thebinary data; and converting the forward error correction binary datainto the non-ternary modulated data.

Example 15. The method of any one of examples 1-14, wherein the receiveris configured to convert the received non-ternary data into binary dataand apply FEC decoding to the binary data.

Example 16. The method of any one of examples 1-15, wherein each of thethree modulated states of the ternary PSK format has non-overlappingtransition curves when detected by a detector in the receiver.

Example 17. The method of any one of examples 1-16, wherein the receiveris geographically remote from the transmitter.

Example 18. A phase shift key (PSK) transmitter comprising: one or moreprocessors; an optical source; and a memory storing instructions that,when executed by the one or more processors, cause the PSK transmitterto perform operations comprising: identify binary data for transmission;generate ternary modulated data from the binary data, the ternarymodulated data being in a ternary PSK format comprising three modulationstates; generate, from the ternary modulated data, non-ternary modulateddata for transmission to a receiver, the non-ternary modulated databeing in a non-ternary PSK format that comprises fewer than threemodulation states or more than three modulation states; andtransmitting, to the receiver, the non-ternary modulated data as lightusing an optical source.

Example 19. The PSK transmitter of example 18, wherein converting theternary modulated data to the non-ternary modulated data comprises usinga phase mapping to map the ternary PSK format to the non-ternary PSKformat.

Example 20. The PSK transmitter of any one of examples 18 to 19, whereinthe receiver is configured to sample the received light at transienttime, the sampling at transient time being performed by ananalog-to-digital converter in the receiver.

Example 21. A phase shift key (PSK) device, comprising: a modulator togenerate ternary modulated data from binary data, the ternary modulateddata being in a ternary PSK format comprising three modulation states; aconverter to convert the ternary modulated data to non-ternary modulateddata for transmission to a receiver, the non-ternary modulated databeing in a non-ternary PSK format that comprises more than threemodulation states; and a transmitter to transmit, to the receiver, thenon-ternary modulated data as light using an optical source.

Example 22. The PSK device of example 21, wherein the converter convertsthe ternary modulated data to non-ternary modulated data using a phasemapping to map the ternary PSK format to the non-ternary PSK format.

Example 23. The PSK device of any of examples 21 or 22, wherein thereceiver is a direct detection based receiver that receives the lightcomprising the non-ternary modulated data.

Example 24. The PSK device of any of examples 21-23, wherein thereceiver is configured to sample the non-ternary modulated data attransient time.

Example 25. The PSK device of any of examples 21-24, wherein thetransmitter is configured to convert the non-ternary modulated data intolight using the optical source, wherein the light is transmitted to thereceiver using a fiber.

Example 26. The PSK device of any of examples 21-25, wherein themodulator comprises a distribution matcher to generate the ternarymodulated data from the binary data.

Example 27. The PSK device of any of examples 21-26, wherein thereceiver is configured to convert the light into ternary modulated dataand convert the ternary modulated data into binary data using an inversedistribution matcher.

Example 28. The PSK device of any of examples 21-27, wherein thenon-ternary modulated data is transmitted to the receiver over anoptical network.

In the foregoing detailed description, the method and apparatus of thepresent inventive subject matter have been described with reference tospecific exemplary embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the present inventivesubject matter. The present specification and figures are accordingly tobe regarded as illustrative rather than restrictive.

What is claimed is:
 1. A method for processing optical data using aphase shift key transmitter, the method comprising: identifying data ina binary format; generating ternary phase shift key data from the datain the binary format, the data being encoded in the ternary phase shiftkey data in three states; generating non-ternary phase shift key datafrom the ternary phase shift key data, the data being encoded in thenon-ternary phase shift key data in a quantity of states other than thethree states; and transmitting the non-ternary phase shift key data to areceiver as light.
 2. The method of claim 1, wherein the non-ternaryphase shift key data encodes the data in a quaternary phase shift keyformat, and the quantity of states is four states.
 3. The method ofclaim 1, wherein the receiver is a direct detection based receiver thatreceives the light comprising the non-ternary phase shift key data. 4.The method of claim 1, wherein the receiver is configured to sample thenon-ternary phase shift key data at transient time.
 5. The method ofclaim 4, wherein sampling at transient time is performed by ananalog-to-digital converter in the receiver, wherein transient timecorresponds to sampling between symbol segments of the non-ternary phaseshift key data.
 6. The method of claim 1, further comprising: convertingthe non-ternary phase shift key data into light using an optical source,wherein the light is transmitted to the receiver using a fiber.
 7. Themethod of claim 1, wherein the ternary phase shift key data is generatedfrom the data in the binary format using a distribution matcher.
 8. Themethod of claim 1, wherein the receiver is configured to convert thelight into ternary phase shift key data and convert the ternary phaseshift key data into the data in the binary format using an inversedistribution matcher.
 9. The method of claim 1, further comprisingconverting the non-ternary phase shift key data into the data in thebinary format.
 10. The method of claim 9, further comprising generatingforward error correction binary data by applying forward errorcorrection coding to the data in the binary format.
 11. The method ofclaim 10, further comprising converting the forward error correctionbinary data into the non-ternary phase shift key data, wherein thereceiver is configured to convert the non-ternary phase shift key datainto the data in the binary format and apply forward error correctiondecoding to the data in the binary format.
 12. The method of claim 1,wherein each of the three states of the ternary phase shift key formathas non-overlapping transition curves when detected by a detector in thereceiver.
 13. The method of claim 1, wherein the non-ternary phase shiftkey data is transmitted to the receiver over an optical network.
 14. Aphase shift key device, comprising: a modulator to generate ternaryphase shift key data from data in a binary format, the data beingencoded in the ternary phase shift key data in three states; a converterto convert the ternary phase shift key data to non-ternary phase shiftkey data, the data being encoded in the non-ternary phase shift key datain a quantity of states other than the three states; and a transmitterto transmit the non-ternary phase shift key data to a receiver.
 15. Thephase shift key device of claim 14, wherein the non-ternary phase shiftkey data encodes the data in a quaternary phase shift key format, andthe quantity of states is four states.
 16. The phase shift key device ofclaim 14, wherein the receiver is configured to sample the non-ternaryphase shift key data at transient time.
 17. The phase shift key deviceof claim 14, wherein the transmitter is configured to convert thenon-ternary phase shift key data into light using an optical source,wherein the light is transmitted to the receiver using a fiber.
 18. Thephase shift key device of claim 14, wherein the modulator comprises adistribution matcher to generate the ternary phase shift key data fromthe data in a binary format.
 19. The phase shift key device of claim 14,wherein the receiver is configured to convert light into ternary phaseshift key data and convert the ternary phase shift key data into data inthe binary format using an inverse distribution matcher.
 20. The phaseshift key device of claim 14, wherein the non-ternary phase shift keydata is transmitted to the receiver over an optical network.